Add script to download fixtures locally

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/117672



Merged-by: Rémy Coutable <remy@rymai.me>
Approved-by: Phil Hughes <me@iamphill.com>
Approved-by: Rémy Coutable <remy@rymai.me>
Approved-by: Lukas 'Eipi' Eipert <leipert@gitlab.com>
Reviewed-by: Rémy Coutable <remy@rymai.me>
Reviewed-by: Lukas 'Eipi' Eipert <leipert@gitlab.com>
Co-authored-by: ddieulivol <ddieulivol@gitlab.com>